/*
 * Copyright 2013-2023 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.alibaba.cloud.nacos.refresh;

import java.math.BigInteger;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.LinkedList;
import java.util.Map;

import com.alibaba.cloud.commons.lang.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


public class NacosRefreshHistory {

    private final static Logger log = LoggerFactory.getLogger(NacosRefreshHistory.class);

    private static final int MAX_SIZE = 20;

    private final LinkedList<Record> records = new LinkedList<>();

    private final ThreadLocal<DateFormat> DATE_FORMAT = ThreadLocal.withInitial(() -> new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));

    private MessageDigest md;

    public NacosRefreshHistory() {
        try {
            md = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            log.error("failed to initialize MessageDigest : ", e);
        }
    }

    /**
     * recommend to use
     * {@link NacosRefreshHistory#addRefreshRecord(java.lang.String, java.lang.String, java.lang.String)}.
     *
     * @param dataId dataId
     * @param md5    md5
     */
    @Deprecated
    public void add(String dataId,
                    String md5) {
        records.addFirst(new Record(DATE_FORMAT.get().format(new Date()), dataId, "", md5, null));
        if (records.size() > MAX_SIZE) {
            records.removeLast();
        }
    }

    public void addRefreshRecord(String dataId,
                                 String group,
                                 String data) {
        records.addFirst(new Record(DATE_FORMAT.get().format(new Date()), dataId, group, md5(data), null));
        if (records.size() > MAX_SIZE) {
            records.removeLast();
        }
    }

    public LinkedList<Record> getRecords() {
        return records;
    }

    private String md5(String data) {
        if (StringUtils.isEmpty(data)) {
            return null;
        }
        if (null == md) {
            try {
                md = MessageDigest.getInstance("MD5");
            } catch (NoSuchAlgorithmException ignored) {
                return "unable to get md5";
            }
        }
        return new BigInteger(1, md.digest(data.getBytes(StandardCharsets.UTF_8))).toString(16);
    }

    static class Record {

        private final String timestamp;

        private final String dataId;

        private final String group;

        private final String md5;

        Record(String timestamp,
               String dataId,
               String group,
               String md5,
               Map<String, Object> last) {
            this.timestamp = timestamp;
            this.dataId = dataId;
            this.group = group;
            this.md5 = md5;
        }

        public String getTimestamp() {
            return timestamp;
        }

        public String getDataId() {
            return dataId;
        }

        public String getGroup() {
            return group;
        }

        public String getMd5() {
            return md5;
        }

    }

}
